Process for polymerizing olefins



Uni ed S es Patent PROCESS FOR POLYMERIZING OLEFINS Robert M. Kennedy,Newtown Square, Pa., assignor to Sun Oil Company, Philadelphia, Pa., acorporation of New Jersey l Application June 25, 1957, Serial No.667,743

6 Claims. (Cl. 260-883) This invention relates to the preparation ofpolymers of normally gaseous olefins, and particularly relates to thepreparation of solid polymers of ethylene, solid polymers of propylene,and solid copolymers of ethylene and propylene.

Normally gaseous olefins can be polymerized by a variety of catalysts. Acatalyst which is especially effective for the polymerization ofnormally gaseous olefins to relatively high molecular weight, solidpolymers is the combination of a lower halide of titanium, such astitanium trichloride and an aluminum trialkyl, such as aluminumtriethyl. This catalyst can be prepared by admixing, for example,titanium tetrachloride and aluminum triethyl in. an inert liquid such asisooctane. On admixing the two components, a finely divided solid phaseis formed as a dispersion in the inert liquid. The solids. of thedispersion are catalysts for polymerizing normally gaseous olefins tosolid polymers. If desired, a lower halide such as titanium trichloridecan be preformed, dispersed in an inert liquid, and an activator such asan aluminum trialkyl added. Such catalysts are deactivated by contactwith water or oxygen, and hence such materials must be excluded fromcontact therewith. In performing the polymerization step, a normallygaseous olefin is contacted with a suspension of the finely dividedsolid in the inert liquid reaction medium and is therein polymerized tosolid polymers. Other materials can'be substituted for titaniumtetrachloride and/or aluminum triethyl, as hereinafter described.

However, in this process the solid catalystparticles become-coated by,or embedded in, the solid polymer product. The separation of polymerfrom catalyst, which is necessary in ,order to obtain a satisfactorypolymer product,-is extremely difiicult. Means heretofore described forseparating catalyst from polymer involve grinding thepolymer-catalyst inthe presence of a catalyst deactivating material such as water oralcohol to expose portions. of the catalyst particles to the action ofsuch deactivating material, and simultaneously or subsequentlyextracting the deactivated catalyst from the polymer such as with analcoholic solution of a mineral acid. This separation means isunsatisfactory in that removal of even a major proportion of thecatalyst is difficult and time consuming, and the catalyst isdeactivated. Hence, such processes of necessity are batch-type andexpensive.

An object of the present invention is to provide a process for thepreparation of solid polymers of normally gaseous olefins, using solidcatalyst particles which are destroyed by contact with water or oxygen,in which the polymer is continuously separated from catalyst withoutdeactivating the catalyst. A specific object of the invention is toprovide a continuous process for the preparation of polypropylene usinga solid catalyst in which the catalyst is not deactivated and in whichthe polymer product is substantially free from catalyst. Other objectsand their achievement in accordance with haws-tre oi t e ii ve e w e p rn h r n r.

It has now been found, in the preparation of solid polymers of normallygaseous olefins involving the use.

of solid catalyst particles, as above described, that by orientingpolymer growth outwardly from a stationary catalyst bed composedessentially of the solid catalyst particles, the polymer chains can becleaved without disturbing the catalyst surface so that the cleavedpolymer is free from contamination by catalyst particles, and thecatalyst is active for further, or continued, olefin polymerization.

Ethylene, propylene, and mixtures of ethylene and pro' pylene are thenormally gaseous olefins which can be polymerized in accordance with theprocess of the pres:

ent invention. Such olefins can be from any source, such as frompetroleum refinery streams, the dehydration of alcohols, or the like.Saturated hydrocarbons such as ethane and propane can be present and actas diluents. For convenience, the process of the invention is hereinlargely described using propylene as illustrative of the normallygaseous olefins which can be used.

In United States patent application Serial Number 624,698, filedNovember 27, 1956, a process using centrifugal force to orient thegrowth of polymers formed from normally gaseous olefins outwardly from acatalyst lyst bed by flowing propylene, or a mixture thereof withanother material such as an inert liquid medium, through a stationarycatalyst bed. The so-oriented polymers can veyor, s forced o gh o e 9 nle 1:0. s

growth or catalyst activity.

be cleaved without interfering with continued polymer" Attention is nowdirected to the accompanying figure which illustrates an embodiment ofthe process of the invention. Numeral 1. represents a conduit havingstationary catalyst bed 2 positioned therein. Screen 4 provides supportfor bed 2. Strands er threads of polymer represented by 5 extendoutwardly from catalyst bed 2. Numeral 6, represents a screw conveyormaintained in conduit 8. Screw conveyor 6 is rotated by shaft 9. Polymerproduct is removed through nozzle 10 having orifice 12. The inert liquidreaction medium and any unreacted or partially reacted olefin is removedfrom conduit 8 through conduit 11.

In operation, a solution of a normally gaseous olefin such as propylenein an inert, liquid reaction medium such as isooctane is introduced intoconduit 1 wherein a it flows downwardly through catalyst bed 2. Becauseof the velocity of the reaction medium through catalyst bed 2, polymergrowth is oriented so that strands or chains of the polymer extenddownwardly from the catalyst bed, passing through the catalyst bedsupport. It appears that the polymerization reaction of the'presentinvention occurs by way of olefin monomers entering into the polymerchain at a location adjacent the catalyst surface, so that cleavage ofpolymer strands does not affect subsequent polymerization, and in theevent that strands are cleaved from the catalyst bed, an activecatalytic surface remains where additional polymerization can occur. Thepolymer fibers continue to grow until they contact screw conveyor 6.Cutting means or the like (not shown) can be combined with the screwconveyer if desired. The screw conveyor conducts the separated polymeralong conduit 8 to the direction of nozzle 10. Substantially all-of theinert reaction medium and unreacted or partially reacted olefin isseparated prior to nozzle 10 such as through conduit 11.

Advantageusly, this separated material is recycled to the process,together with make-up ingredients as necessary. The polymer, underpressure from the screw con- Patented Jan. 12,19 0

a desired form of the polymer product can be prepared. However, theshape of nozzle does not form a part of this invention, and the nozzlecan be omitted if desired.

-Various alterations, modifications and additions to the apparatus asdescribed will be apparent to those skilled a sintered glass disk as asupport. An inert, liquid reaction medium is introduced into thereaction vessel above and in contact with the catalyst bed. Propylene isthen introduced into the reaction vessel below the catalyst bed. Thesintered glass catalyst bed support serves to difiuse thepropylenethroughout the catalyst bed. The velocity of the propylene through thecatalyst bed orients polymer growth upwardly from the catalyst bed sothat the polymer chains extend into the inert reaction medium. Thepolymer chains extending upwardly from the catalyst bed can be removedcontinuously or intermittently such as by cutting or other means. Insome instances sufiicient turbulence can be obtained so that afterreaching a certain length, the polymer chain breaks and floats to'thesurface of the reaction medium where it is removed from the process. Inthis embodiment, the space below the catalyst can be filled or partiallyfilled with inert,-liquid reaction medium, or more preferably by thepropylene passing upwardly through the bed. The quantityof propylenepassed through the catalyst bed must be sufficient so that the velocitythereof orients polymer growth, i.e., an excess of propylene must beused. Unreacted propylene can be recovered or recycled to the process.

-'I'he'catalyst bed is formed on a support therefor. The catalysts ofthe inventionv are solid particles formed by the reduction of a halideor salt of a metal of the left hand side of groups IV, V or VI of theperiodic table. Preferably, a subhalide or salt of titanium, zirconium,hafnium, vanadium, niobium, chromium, molybdenum or tungsten is used.The metal of the metal compound must be in a valence state other thanits highest valence state. The reduction of such a metal compound, suchas titanium tetrachloride, can be accomplished by any convenient means,such as by contacting with a dispersion of an alkali metal in a solvent,or by contacting with an aluminumtrialkyl. In any event, it is necessarythat anactivator, such as an aluminum trialkyl, be present together'withthe catalyst, and it is convenient in many instances to employ such acompound as both the reducing agent and the activator. However, the useof a prereduced compound, such as TiCl TiCl or a mixture thereof,together with an activator, gives excellent results. Materials which canbe used as the activator, in addition to aluminum trialkyls, includeother metal alkyls, metal hydrides, metal borohydrides, and alkyl metalhalides. Suitable metal alkyls include alkyl derivatives of aluminum,zinc, berylium, chromium, magnesium, lithium and lead. Aluminumtriethyl, aluminum triisopropyl, aluminum triisobutyl, and the magnesiumand Zinc analogues thereof give good results in the process and arepreferred, but metal alkyls having up to about 12 carbon'atoms-in thealkyl groups can be used with good results. Alkali metal alkyls such asn-butyllithium, methylsodium, butylsodium, phenylisopropylpotassium, andthe like,- also illustrate metal alkyls that give good results in theprocess. Metal hydrides which can be used as polymerization activatorsinclude, for example,

lithium hydride, lithium aluminum hydride and sodium a'ndpotassiumborohydride illustrate" the borohydrides which can be used.Alkyl metalhalidcs which canbe used as Grignard reagents such asmethylmagnesium bromide, ethylmagnesium chloride, phenylmagnesiumbromide, and the like.

The catalyst bed can be formed by positioning a catalyst support such asa wire mesh, sintered glass plate, or a perforated metal disk within theconduit in which polymerization is performed. A slurry of solid catalystparticles is then passed through the support so that the solid catalystparticles are collected on the support as a bed. It is advantageous toposition a support above the bed so that the solid catalyst particlesare held in position in the bed. If desired, the catalyst can bedeposited on a carrier such as alumina, carbon, silicaaluminacompositions, or the like. Such deposition can be accomplished, forexample, by impregnating the support with titanium tetrachloride, or asolution thereof in a solvent, andcontacting the impregnated carrierwith a reducing agent such as an aluminum trialkyl. The activator forthe catalyst particles, as above described, is preferably introduced as,a solution together with the olefin to be polymerized in the inert,liquidreaction medium.v However, periodic activation rather thancontinuous activation can be used with good results. The quantity ofactivator to use can be varied substantially and good results obtained.It is preferred initially to contact the catalyst bed with a quantity ofactivator so that the moleratio of activator to catalyst is from about0.5:1 to 10:1, and to thereafter introduce,-continuously orintermittently, a small quantity of the activator to maintain a rapidrate of polymerization.

The polymerization reaction is performed under polymerizing conditionsof temperature and pressure. The temperature canbe varied from about 0C. to about 150 C., and ambient'temperature gives good results, but

preferably the temperature ismaintained in the range" of from about 60C. to C. The pressure is' ad vanta'geously atmospheric or above, and apressure of from about 10 to 5,000 p.s.i.g. (pounds per square inchgauge) gives good results when the olefin dissolved in reaction mediumis passed through the catalyst bed, since' the solubility of the olefinin the reaction medium is increased by the elevated pressure. Thepressure must be sufficient to maintain the inert, liquid reactionmedium in the liquid phase at the temperature employed.

Saturated hydrocarbons are preferably used as the inert, liquid reactionmedium. Parafiins such as the hexanes, heptanes, octanes, decanes, andmixtures thereof give good results. Cycloparaffins, such as thecyclopentanes, and cyclohexanes, and mixtures thereof with each otherand with paraffins also give good results.

The following example illustrates an embodiment of the process of theinvention in which parts refers to parts by weight.

A sintered glass disk about 2 inches in diameter and about A inch thickwas positioned in a glass'tube' having a diameter of about 2 inches.After drying and removing oxygen from the apparatus, 1.27 parts oftitanium trichloride were introduced into the glass tube to form a bedabout inch thick on the sintered glass support, this introduction beingaccomplished under a nitrogen atmosphere. A 325 mesh screen (U.S.series) of copper wire was positioned over the catalyst bed. Into thetube" above the catalyst were introduced 350 cc. of n-heptane, and 10.1cc. of a 10% solution of aluminum triisobutyl in n-heptane. Thetemperature of the apparatus and contents was adjusted to 71 C.Propylene was then' introduced into the bottom of the glass tube. Thepropylenepassed upwardly through the sintered glass disk and thecatalyst bed. The pressure'of the'apparatus was adjusted to 73 p.s.i.g.After about 15 minutes, polymer chains appeared growing upwardly fromthe" catalyst bed, through the screen, and-into then-heptanef: The rateof ropyl ne addition was regulated so that a concentration thereof ofabout 15 mole percent iir then-lreptane" was maintained, which amountwas an excess sufficient to cause vigorous agitation while passingthrough the nheptane. After 3 /3 hours, a multiplicity of long polymerchains had grown upwardly into the n-heptane. A portion of these chainswere cleaved by the agitation of the propylene, and passed to the top ofthe apparatus. Such cleavage did not interfere with subsequentpolymerization, and the so-removed polymer formed a portion of thepolymer product. The polymer product was a white, crystalline solidhaving a melting point of about 164 C. and was substantially free ofcontamination by the metals of the catalyst.

As above described, polymerization can be continued over a long periodof time with the polymer preferably continuously removed from thecatalyst bed. However, after long operation, the catalyst bed may becomefouled by polymer so that passage therethrough of liquid and/ or gas isdifiicult. In such event, operation is discontinued and a solvent, whichis preferably a saturated hydrocarbon, passed through the bed at anelevated temperature of say from about 150 C. to 200 C., and a pressuresufficient to maintain the solvent in the liquid phase. The polymeradhered to the catalyst bed is thereby dissolved and is removed from thebed. Saturated hydrocarbons such as the heptanes, octanes, decanes,cyclohexanes, decahydronaphthalene and the like give good results. Afterregenerating the actalyst bed by washing, a quantity of activator shouldbe contacted with the catalyst bed before continuing the polymerization.

The polymer products of the invention are useful in the form of thinfilms for packaging, for preparing conduits for transporting liquids, ascontainers for corrosive liquids, and the like. Such articles can beprepared by extrusion, molding, or other fabrication means.

The invention claimed is:

1. Process for the preparation of solid polymers of normally gaseousolefins which comprises flowing, under polymerizing conditions, anormally gaseous olefin through a stationary bed of solid catalystparticles of a metal subhalide selected from the group consisting of thesubhalides of the metals of groups IV, V and VI of the periodic table incontact with an aluminum trialkyl for the catalyst particles and aninert, liquid reaction medium, whereby polymer chains of said normallygaseous olefin extending outwardly from said catalyst bed in thedirection of olefin flow are formed, cleaving the soformed polymerchains from the catalyst bed and recovering the polymer.

2. Process according to claim 1 wherein said normally gaseous olefin isethylene. I

3. Process according to claim 1 wherein said normally gaseous olefin ispropylene.

4. Process according to claim 1 wherein said normally gaseous olefin isa mixture of ethylene and propylene.

5. Process for the preparation of solid polymers of propylene whichcomprises flowing, under polymerizing conditions, propylene through astationary bed of solid catalyst particles consisting essentially of ametal subhalide selected from the group consisting of the subhalides ofthe metals of groups IV, V, and VI of the periodic table in contact withan aluminum trialkyl and an inert liquid reaction medium whereby chainsof polypropylene extending outwardly from the actalyst bed in thedirection of propylene flow are formed, and cleaving said chains torecover polypropylene.

6. Process according to claim 5 wherein the catalyst is titaniumtrichloride.

References Cited in the file of this patent UNITED STATES PATENTS1,985,457 Nutting et al. Dec. 25, 1934 2,088,929 ScharfiE et al. Aug. 3,1937 2,392,798 Kleiss Jan. 8, 1946 2,416,003 Guyer Feb. 18, 19472,459,480 Welty et al. Jan. 18, 1949 2,727,023 Evering et al. Dec. 13,1955 FOREIGN PATENTS 538,782 Belgium Dec. 6, 1955

1. PROCESS FOR THE PREPARATION OF SOLID POLYMERS OF NORMALLY GASEOUSOLEFINS WHICH COMPRISES FLOWING, UNDER POLYMERIZING CONDITIONS, ANORMALLY GASEOUS OLEFIN GHROUGH A STATIONARY BED OF SOLID CATALYSTPARTICLES OF A METAL SUBHALIDE SELECTED FROM THE GROUP CONSISTING OF THESUBHALIDES OF THE METALS OF GROUP IV, V AND VI OF THE PERIODIC TABLE INCONTACT WITH AN ALUMINUM TRIALKYL FOR THE CATALYST PARTICLES AND ANINERT, LIQUID REACTION MEDIUM, WHEREBY POLYMER CHAINS OF SAID NORMALLYGASE-